This invention relates to a lightweight clamp and in particular to a clamp, that, when removably attached to parallel sided kerf cutting tips brazed on to the attack face of the gullet on a saw blade blank, can be manually rotated by use of a torque wrench to determine the strength of the braze connection.
Commercial lumber production utilizes high-speed saws, many of which have replaceable, pre-sharpened carbide kerf tips that are brazed oil to the attack face of the saw blade gullet. Such tips are subject to wear and dulling and on occasion, separation from the saw blade. These blades are re-sharpened at regular intervals and replaced as necessary. Separation of the kerf tip from a saw blade is a generally unexpected and unwelcome occurrence, resulting in the loss of production until the saw blade is replaced.
Quality testing of the braze strength between saw blade and kerf tip or kerf cutter (used alternatively herein) is therefore desirable, firstly for braze quality control, ensuring that separation due to inadequate braze strength is all but eliminated and secondly, to test a number of cutters on a blade where cutter separation has occurred, to determine if braze strength was a factor in the cutter separation.
Such cutters are usually provided per-tinned with high strength alloy and may be readily replaced on site, by positioning the replacement kerf cutter against the clean attack face of the saw blade and applying sufficient heat to melt the braze material.
Previously, the techniques for testing the strength of the braze connection between the saw blade and the kerf cutter have relied more upon operator judgment rather than on empirical data. In many cases the failure may not occur exactly at the bond between the saw plate and the saw tip. This can break or bend the saw plate or the saw tip and prevent the ability to inspect the bond area. For example, one technique requires that the cutter be gripped by vice grips or pliers and as heat is gradually applied to the area of the cutter, the vice grips are used to apply a rotational force on the cutter generally parallel to the axis of rotation of the saw. Upon separation of the cutter a visual inspection is made to determine the quality of the braze connection.
In another example, a block of hickory wood or UHMW material is used to strike the cutter in a direction generally parallel to the axis of rotation of the saw blade. The effect the blow has upon the cutter is then determined by eye.
A further example is that of securing the saw in a vice and applying a lateral pressure against the cutter by a hydraulic ram. The pressure required to cause cutter separation can then be observed.
The present invention is a braze strength testing clamp, which can be placed over a tooth on a saw blade, for example a circular saw. A through notch formed in the under side of the housing permits it to be positioned over and aligned with the braze-on saw tip or kerf cutting tip. Clamping means, secured to the housing, in the form of at least one movable jaw, can be brought into firm contact with the sides of a cutting tip mounted to the saw blade. A torque wrench is removably attachable to the housing.
Non-destructive testing of the braze connection between the cutting tip and the saw is possible by firstly noting the predetermined tabular value for the braze strength appropriate for the saw blade thickness and the tooth size being tested and manually loading the torque wrench, in an appropriate manner, until that value is achieved. Should the braze connection hold, the braze connection then is obviously satisfactory. On the other hand should the cutter tip separate under loading before the recommended force is applied then the braze is faulty and further testing such as microscopic examination and measurement of the braze thickness and anchor fillet is undertaken.
Destructive testing is carried out in a similar manner, however, such tests will determine the maximum strength of the braze connection.
In summary, the present invention is a device mountable onto the head of a torque wrench for testing the braze strength of replaceable kerf tips, the device includes a clamp supporting member for clamped mounting, at a first end thereof, to a braze-on saw tip brazed to a saw blade tooth, and for mounting, at an opposite second end of said member, to the head of the torque wrench. A clamp, for rigidly clamping the braze-on saw tip between opposed facing jaws of said clamp, is mounted to the clamp supporting member so as to orient said jaws on opposite sides of an axis of rotation of the head of the torque wrench when the head is mounted to said second end of said member.
The clamp supporting member may be an elongate bar or housing or otherwise adapted for holding a clamp so that a moveable jaw, which is at least one of the opposed facing jaws, may be translated, for example in a direction generally parallel to the axis of rotation of the saw blade, so as to clamp the braze-on saw tip on the opposite sides of the braze-on saw tip, that is the opposite sides of the braze-on saw tip generally parallel to the opposite sides of the saw blade. The braze-on saw tip is thereby clamped within a clamping space defined between the jaws. A selectively actuable actuator is provided for actuating the moveable jaw between a release position retracted away from an opposite opposed facing jaw, which may be fixed to the clamp supporting member or also moveable, and a clamp engaging position wherein the moveable jaw is translated, for example either slidably or pivotally, into clamping engagement with a braze-on saw tip between the jaws or, in the absence of the braze-on saw tip, into sufficiently close proximity for clamping upon the presence of the braze-on saw tip.
The clamp supporting member may be adapted, for example by waisting of the member, so as to not interfere either with the clamping space or with adjacent saw blade teeth and their corresponding braze-on saw tips on teeth adjacent to a tooth and braze-on saw tip clamped in said clamp clamping space. The clamp supporting member has a selectively engageable torque wrench mounting member, for example a bolt head, mounted to said member for releasable engagement with the head of the torque wrench, wherein said wrench mounting member has an axis of rotation which is co-axial with the axis of rotation of the head of the torque wrench when the torque wrench is mounted on the wrench mounting member. The axis of rotation of the mounting member also generally bisects the clamping space when the moveable jaw is in the clamp engaging position, or otherwise so as to be substantially coaxial with an axis of the braze-on saw tip which is substantially parallel to the brazing surface common to the clamped braze-on saw tip and the saw blade tooth.
The method of the present invention for testing the braze strength of a replaceable kerf tip brazed onto the tooth of a saw blade includes the steps of:
a) providing a braze strength testing tool as described above,
b) mounting the torque wrench onto the torque wrench mount,
c) mounting the jaws over the kerf tip and clamping the jaws onto the kerf tip so as to intersect the axis of rotation of the head of the torque wrench generally collinearly with a long axis of the kerf tip parallel to the braze joint, and
d) rotating the torque wrench about it""s axis of rotation and monitoring the torque level indicated by the torque wrench.